Wastewater generated by municipalities and industries water is commonly collected and routed to a treatment facility for the removal of a variety of physical, chemical and biological pollutants prior to being discharged into a receiving body of water. To effect the necessary treatment, many public and private treatment facilities employ both physical and biological treatment methods. Physical methods—including screening, grinding and physical settling processes—are effective for the removal of larger and heavier solids in the wastewater. However, lighter, smaller solids and other soluble pollutants in the wastewater resist removal by physical methods. For these pollutants, biological treatment methods such as activated sludge and trickling filters are commonly employed.
Regulation of pollutant discharges from municipal wastewater treatment systems has become more stringent in recent years. In response, many municipalities have deployed new wastewater treatment systems or retrofitted existing systems to reduce pollutant discharge. Pollutants can be many forms with the most common being Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), ammonia, total nitrogen, nitrate, nitrite and phosphorous.
Biological treatment systems, such as conventional activated sludge systems and membrane bioreactors are one method to reduce the pollutants in a wastewater influent. The term “influent” refers to wastewater or other liquid—raw (untreated) or partially treated—flowing into a reservoir, basin, treatment process or treatment plant or treatment facility. Biological treatment systems are designed and operated to retain an adequate amount of activated sludge such that the pollutant load contained in the water treated by the system will be adequately reduced. The net amount defined as weight or mass of waste activated sludge produced is related to the Solids Retention Time (SRT) of the system. The minimum SRT required to treat various pollutants under various conditions is generally well known. Conventional activated sludge systems retain activated sludge by the use of settling or clarification devices and can maintain adequate SRTs to treat pollutants provided that the flow of the activated sludge concentration and settleability of the activated sludge going to the settling basins or clarifiers are within reasonable limits set by design parameters, which depend upon the area of the settling basins or clarifiers and the characteristics of the activated sludge. Membrane bioreactor systems retain the activated sludge by the use of membrane filtration equipment and can operate successfully at significantly higher activated sludge concentrations than typical for conventional activated sludge systems, but are more limited in their ability to process occasional high flow rates.
When pollutant loading or hydraulic capacity limits are reached, treatment facilities face the risk of permit limit violations, the possibility of Federal or State enforcement action, and restrictions or prohibitions on domestic and industrial growth within the collection system service area of the treatment works. Typically, wastewater treatment facilities undergo physical expansion to meet the needs of increased hydraulic loading. But, physical expansion is expensive and often requires additional land that may not be available adjacent to existing facilities, particularly in large cities where land is more expansive.
Therefore, it is desirable to find a way to increase volumetric or mass pollutant loading and hydraulic capacity without the need for physical plant expansion. A significant advantage of the present invention over prior art methods of sludge processes is that volumetric pollutant loading can be substantially increased with addition of the Biofermentor to existing physical facilities. In addition, it is also a feature and advantage of the present invention that the enhanced sludge process produces a biological sludge with improved settling characteristics. Improved settling characteristics allow increases in hydraulic loading without requiring an increase in the size of the physical elements of the activated sludge system because the net sludge wastage and/or production is lower. Another advantage is a reduction in operating costs, such as chemicals, manpower, energy, and transportation because there is less biological sludge to be handled in the sludge handling processes and disposed of, which typically represents 40-50% of the operating costs of wastewater treatment facility. By the same token, a new wastewater operating costs of a wastewater treatment facility. By the same token, new wastewater treatment plants can be constructed in smaller sizes, with much reduced need for sludge handling facilities and hence at lower capital costs than known systems. For existing wastewater treatment systems requiring upgrades it may be possible to eliminate the need for capital expansion or delay parts or all of the expansion. Additionally, the time between wasting biological sludge may be extended from the activated sludge process to an aerobic or anaerobic digester by 25-50%, and from that process by 25-50% to the dewatering step, such as drying bed, filter press or centrifuge. This additional time means less manpower requirements, less equipment, less power usage and less chemical usage.